Prior systems known to us for proportionately blending powdered or granular concentrated color pigment with extruded plastic resin compounds to produce a wide variety of colors and shades have been limited to preblending the color pigment and resin on a batch basis because available metering equipment did not deliver accurately and continuously the required small amounts of color pigment. Moreover, such prior equipment is not capable of accurately regulating the continuous delivery of the required low level amounts, for example, 5 to 10 grams per minute, so as to vary the proportion of color pigment to the amount of resin moving through the extruder.